Hyung-Jin Lim

Route Optimization in Nested NEMO: Classification, Evaluation, and Analysis from NEMO Fringe Stub Perspective

Mobile IP is the basic solution to providing host mobility, whereas network mobility (NEMO) refers to the concept of the collective mobility of a set of nodes. The NEMO basic support protocol has been proposed in IETF as a first solution to the problem of network mobility. The main limitation of this basic solution is that it forces triangular routing, i.e., packets are always forwarded through the home agent (HA), following a suboptimal path. This is because each sub-NEMO obtains a care of address (CoA) that belongs to the home prefix of its parent mobile router. Such a CoA is not topologically meaningful in the current location, since the parent mobile router could also be away from home, and hence, packets addressed to the CoA are forwarded through the HA of the parent NEMO. To solve this problem, various extended proposals, with differing approaches and goals, exist for route optimization (RO) in NEMO applications. Their influences on the RO performance have been evaluated by classifying the detailed operations performed within the nested NEMO network, and then each category is analyzed in detail. The modeling of the detailed RO operation is intended to quantify the tradeoffs between the different approaches in order to provide a basis for the selection decision. In particular, the proposed grouping of the different proposals, based on their address configuration strategy, clarifies their similarities and differences, and provides some useful insights into the various methods that have been developed. In conclusion, it is suggested that, when choosing a solution for deploying NEMO, the designer has to balance his choices between the different pros and cons, and the different cases of application that are derived in this paper.

On Efficient Core Selection for Reducing Multicast Delay Variation under Delay Constraints

With the proliferation of multimedia group applications, the construction of multicast trees satisfying the Quality of Service (QoS) requirements is becoming a problem of the prime importance. An essential factor of these real-time application is to optimize the Delay- and delay Variation-Bounded Multicast Tree (DVBMT) problem. This problem is to satisfy the minimum delay variation and the end-to-end delay within an upper bound. The DVBMT problem is known as NP-complete problem. The representative algorithms for the problem are DVMA, DDVCA, and so on. In this paper, we show that the proposed algorithm outperforms any other algorithm. The efficiency of our algorithm is verified through the performance evaluation and the enhancement is up to about 13.5% in terms of the multicast delay variation. The time complexity of our algorithm is O(mn 2 ) which is comparable to well known DDVCA.

Optimizing Access Point Allocation Using Genetic Algorithmic Approach for Smart Home Environments1

In recent years, high-bandwidth and low-cost wireless technologies have emerged as a competitive element, enabling the smart home environment. On the other hand, with the increasing demands for various services, the current access point allocation schemes give rise to significant challenges for a stable connection service, bandwidth and load distribution. In this paper, we present an optimal access point allocation scheme based on genetic algorithm that attempts to optimize multiple parameters, such as bandwidth, and load-balancing requirements. The proposed allocation scheme provides a set of approximately efficient solutions, which allows a wireless user to choose an access point based on its capacity and load balancing, not only regarding its signaling strength or service set identifier. The simulation results are provided to demonstrate the impact of the proposed optimization procedure on overall system performance in terms of connection distribution, load balancing and call dropping probability.

Preventing Out-of-Sequence Packets on the Route Optimization Procedure in Proxy Mobile IPv6

Proxy mobile IPv6 is one of network-based mobility support protocols which does not require a mobile host to be involved in mobility support signaling. Even though proxy mobile IPv6 has many advantages than client-based mobility support protocols such as mobile IPv6, unfortunately, it may cause an out-of-sequence problem during its route optimization procedure. Thus, in this paper, we develop an estimation function for an out- of-sequence time period and reveal the out-of-sequence problem caused by the route optimization procedure. Then we propose a scheme which minimizes the arrival of out-of-sequence packets to the mobile host and analyze the impact of out-of-sequence packets. The performance evaluation results demonstrate that the traffic rate and out-of-sequence time period mainly have an effect on the out-of-sequence problem.

Follicular cholangitis mimicking hilar cholangiocarcinoma

A 61-year-old man with intermittent periumbilical pain and high liver enzyme levels underwent spiral computed tomography of the abdomen with intravenous contrast medium enhancement. Abdominal computed tomogram showed wall thickening of both intrahepatic ducts and proximal common hepatic duct with enhancement. Direct cholangiogram showed severe smooth strictures from the common hepatic duct to both intrahepatic ducts. The findings were interpreted as hilar cholangiocarcinoma. The pathologic findings after surgical resection were consistent with follicular cholangitis.

Reducing Communication Overhead for Nested NEMO Networks: Roaming Authentication and Access Control Structure

In this paper, we present a practical public key certificate structure that is combined with an authentication protocol for roaming across different wireless Internet service providers (ISPs). The design rationale is to enable the mutual authentication between the roaming mobile device (MD) and the visited network to be locally performed without invoking the MDs home ISP. The mutual authentication ensures that the visited network has authenticity as well as a mechanism for establishing the appropriate revenue stream for the roaming MD. The proposed scheme guarantees that the overhead associated with the authentication time is significantly reduced and that the impact of this overhead on the roaming MD is also minimized, although the nested depth of the network mobility is increased. In this paper, we use analytical comparisons to show that the proposed scheme creates less overhead than that of the previous approaches in terms of security and communication performance.

New binding update method using GDMHA in hierarchical mobile IPv6

Mobile IPv6 is a protocol that guarantees mobility of mobile node within the IPv6 environment. However current Mobile IPv6 supports simple the mobility of the mobile nodes and does not offer any special mechanism to reduce the handoff delay. For the purpose of reducing the handoff delay, Hierarchical Mobile IPv6 has been studied. However Hierarchical Mobile IPv6 supports the micro mobility only in the area managed by mobility anchor point. Therefore, the handoff delay problem still has been unsolved when mobile node moves to another mobility anchor point. In this paper, we propose GDMHA (Geographically Distributed Multiple HAs) mechanism to provide macro mobility between the mobility anchor points. Using this mechanism, a mobile node performs Binding Update with the nearest Home Agent, so that the delay of Binding Update process can be reduced. It also reduces the handoff delay.

An analysis and evaluation of policy-based network management approaches

This paper provides an analytical framework for comparison between centralized and distributed models of policy-based network management (PBNM). Policy-based networks are being deployed in a variety of applications, in which the policy-enabled architecture may provide appropriate performance control depending on the particular application being used. Therefore, in this paper, each PBNM model is evaluated based on the performance and scalability provided when a policy is provisioned. Our metrics include a qualitative evaluation of the policy provisioning time, the amount of traffic measured between the PBNM components and PDP utilization. Each approach has its own merits and demerits depending on the particular application requirement. We highlight the fact that an appropriate architecture needs to be introduced, in order to optimize the PBNM deployment. The PBNM modeling framework presented in this paper is intended to quantity the merits and demerits of the currently available methodologies.

Performance evaluation of public key based mechanisms for mobile IPv4 authentication in AAA environments

With the proliferation of mobile terminals, use of the Internet in mobile environments is becoming more common In order to support mobility in these terminals, Mobile IPv4 was proposed, representing the standard in IPv4 environments In this environment, authentication should be mandatory, because mobile terminals can utilize Internet services in all foreign domains Mobile IPv4 provides symmetric key based authentication using the default HMAC-MD5 However, symmetric key based authentication creates a problem, when it comes to key distribution In order to solve this problem, public key based authentication mechanisms were proposed In this paper, the performance of each of these mechanisms is evaluated The results demonstrate that, among these mechanisms, partial certificate based authentication results in superior performance, and certificate based authentication results in the worst performance This paper creates the possibility of public key based authentication mechanisms being used for future mobile terminal authentication, although current public key based authentication mechanisms result in lower performance than symmetric key based authentication.

Mobile IP using private IP address through stateful network address translation

Mobile networking is becoming popular. The increase in mobile communication makes the lacking problem in number of addresses for IPv4 more serious. To solve this problem, this paper proposes an approach to fulfill a mobile JP protocol by using a stateful NAT (Network address Translation) technology. This approach is able to communicate through information sharing by the NAT address mapping between HA and FA. Therefore, the preferred protocol is not requiring an additional procedure between HA and FA for processing, which relate the mobiIity and its showing a normal procedure of the mobile IP. This paper presents a detailed design of the statful NAT approach.